common: add qmat::transpose()

include/common/qvec.hh

@@ -984,6 +984,17 @@ public:
         }
         return res;
     }
+
+    [[nodiscard]] constexpr qmat<T, NCol, NRow> transpose() const
+    {
+        qmat<T, NCol, NRow> res;
+        for (size_t i = 0; i < NRow; i++) {
+            for (size_t j = 0; j < NCol; j++) {
+                res.at(j, i) = at(i, j);
+            }
+        }
+        return res;
+    }
 };
 
 // Fmt support

tests/test_common.cc

@@ -294,3 +294,21 @@ TEST_SUITE("common")
         CHECK(texture->height_scale == 1);
     }
 }
+
+TEST_SUITE("qmat")
+{
+    TEST_CASE("transpose")
+    {
+        // clang-format off
+        auto in = qmat<float, 2, 3>::row_major(
+            {1.0, 2.0, 3.0,
+             4.0, 5.0, 6.0});
+        auto exp = qmat<float, 3, 2>::row_major(
+            {1.0, 4.0,
+             2.0, 5.0,
+             3.0, 6.0});
+        // clang-format on
+
+        CHECK(in.transpose() == exp);
+    }
+}